The method and apparatus concerns a method for improved fresh air supply in a cooking apparatus and a cooking apparatus with an inner housing defining a cooking chamber as well as a fan chamber (separated from the cooking chamber via at least one flow guide element) for a fan with a fan wheel impeller which comprises primary blades on its side facing the first flow guide element and auxiliary blades on its side facing the wall (in particular back wall) of the inner housing through which the axle of the fan wheel passes to connect with a motor arranged outside of the inner housing. The fan wheel is provided for the circulation of cooking atmosphere and/or suction (intake) of fresh air into the inner housing via a fresh air channel whose mouth runs into the inner housing through the aforesaid wall of the same separated from the axle of the fan wheel.
Such cooking apparatuses are known in the prior art, see for example European Application 0 386 862 B1. They represent what are known as circulation air cooking apparatuses that allow an at least temporary fresh air supply to adjust desired climate proportions in the cooking chamber. For this purpose, fresh air is typically conveyed from a kitchen atmosphere into a cooking chamber of the cooking apparatus in order to displace portions of a cooking atmosphere, whereby the fresh air fraction of the aforesaid cooking atmosphere is increased while the fraction of other components such as water vapor, carbon dioxide, aromatic compounds and food-specific outgases is reduced. In such circulation cooking apparatuses in which the cooking atmosphere is significantly rotated via primary blades of a fan, a negative pressure for the take-up of fresh air via a fresh air channel is forced using auxiliary blades rotating with the primary blades and lying opposite the same. However, due to the scarce space ratios in a cooking device, it is sometimes not possible to place the mouth of the fresh air channel in the inner chamber (comprising the cooking chamber) of the cooking apparatus in axial proximity to the fan wheel where (in principle) optimal pressure ratios prevail. This has the disadvantage that now no maximum negative pressure is available as a driving force for the intake of the fresh air.
Furthermore, specified in DE 103 39 099.5 (not previously published) by the applicant is a cooking apparatus that ensures an improved fresh air supply in that the, so to speak, blind, mutually rotating air and/or cooking atmosphere is or are directed over at least one constriction on the back side of a fan wheel, thus on the side opposite the primary blades (which side is equipped with auxiliary blades) during each rotation of the fan wheel, such that there a streamline compression occurs. This streamline compression is accompanied with a pressure reduction given nearly isochoric state changes.